The field of the present invention relates to the delivery of energy impulses (and/or fields) to bodily tissues for therapeutic purposes. The invention relates more specifically to devices and methods for treating conditions associated with gastroparesis, functional dyspepsia, and functional gastrointestinal disorders generally. The energy impulses (and/or fields) that are used to treat those conditions comprise electrical and/or electromagnetic energy, delivered non-invasively to the patient.
The use of electrical stimulation for treatment of medical conditions is well known. For example, electrical stimulation of the brain with implanted electrodes has been approved for use in the treatment of various conditions, including pain and movement disorders such as essential tremor and Parkinson's disease.
Another application of electrical stimulation of nerves is the treatment of radiating pain in the lower extremities by stimulating the sacral nerve roots at the bottom of the spinal cord [Paul F. WHITE, Shitng Li and Jen W. Chiu. Electroanalgesia: Its Role in Acute and Chronic Pain Management. Anesth Analg 92(2001):505-513; U.S. Pat. No. 6,871,099, entitled Fully implantable microstimulator for spinal cord stimulation as a therapy for chronic pain, to WHITEHURST, et al].
The form of electrical stimulation that is most relevant to the present invention is vagus nerve stimulation (VNS, also known as vagal nerve stimulation). It was developed initially for the treatment of partial onset epilepsy and was subsequently developed for the treatment of depression and other disorders. The left vagus nerve is ordinarily stimulated at a location within the neck by first surgically implanting an electrode there and then connecting the electrode to an electrical stimulator [U.S. Pat. No. 4,702,254 entitled Neurocybernetic prosthesis, to ZABARA; U.S. Pat. No. 6,341,236 entitled Vagal nerve stimulation techniques for treatment of epileptic seizures, to OSORIO et al; U.S. Pat. No. 5,299,569 entitled Treatment of neuropsychiatric disorders by nerve stimulation, to WERNICKE et al; G. C. ALBERT, C. M. Cook, F. S. Prato, A. W. Thomas. Deep brain stimulation, vagal nerve stimulation and transcranial stimulation: An overview of stimulation parameters and neurotransmitter release. Neuroscience and Biobehavioral Reviews 33 (2009):1042-1060; GROVES D A, Brown V J. Vagal nerve stimulation: a review of its applications and potential mechanisms that mediate its clinical effects. Neurosci Biobehav Rev 29(2005):493-500; Reese TERRY, Jr. Vagus nerve stimulation: a proven therapy for treatment of epilepsy strives to improve efficacy and expand applications. Conf Proc IEEE Eng Med Biol Soc. 2009; 2009:4631-4634; Timothy B. MAPSTONE. Vagus nerve stimulation: current concepts. Neurosurg Focus 25 (3,2008):E9, pp. 1-4; ANDREWS, R. J. Neuromodulation. I. Techniques-deep brain stimulation, vagus nerve stimulation, and transcranial magnetic stimulation. Ann. N. Y. Acad. Sci. 993(2003):1-13; LABINER, D. M., Ahern, G. L. Vagus nerve stimulation therapy in depression and epilepsy: therapeutic parameter settings. Acta. Neurol. Scand. 115(2007):23-33].
Many such therapeutic applications of electrical stimulation involve the surgical implantation of electrodes within a patient. In contrast, devices used for the medical procedures that are disclosed herein do not involve surgery. Instead, the present devices and methods stimulate nerves by transmitting energy to nerves and tissue non-invasively. A medical procedure is defined as being non-invasive when no break in the skin (or other surface of the body, such as a wound bed) is created through use of the method, and when there is no contact with an internal body cavity beyond a body orifice (e.g, beyond the mouth or beyond the external auditory meatus of the ear). Such non-invasive procedures are distinguished from invasive procedures (including minimally invasive procedures) in that the invasive procedures insert a substance or device into or through the skin (or other surface of the body, such as a wound bed) or into an internal body cavity beyond a body orifice.
For example, transcutaneous electrical stimulation of a nerve is non-invasive because it involves attaching electrodes to the skin, or otherwise stimulating at or beyond the surface of the skin or using a form-fitting conductive garment, without breaking the skin [Thierry KELLER and Andreas Kuhn. Electrodes for transcutaneous (surface) electrical stimulation. Journal of Automatic Control, University of Belgrade 18(2,2008):35-45; Mark R. PRAUSNITZ. The effects of electric current applied to skin: A review for transdermal drug delivery. Advanced Drug Delivery Reviews 18 (1996) 395-425]. In contrast, percutaneous electrical stimulation of a nerve is minimally invasive because it involves the introduction of an electrode under the skin, via needle-puncture of the skin.
Another form of non-invasive electrical stimulation is magnetic stimulation. It involves the induction, by a time-varying magnetic field, of electrical fields and current within tissue, in accordance with Faraday's law of induction. Magnetic stimulation is non-invasive because the magnetic field is produced by passing a time-varying current through a coil positioned outside the body. An electric field is induced at a distance causing electric current to flow within electrically conducting bodily tissue. The electrical circuits for magnetic stimulators are generally complex and expensive and use a high current impulse generator that may produce discharge currents of 5,000 amps or more, which is passed through the stimulator coil to produce a magnetic pulse. The principles of electrical nerve stimulation using a magnetic stimulator, along with descriptions of medical applications of magnetic stimulation, are reviewed in: Chris HOVEY and Reza Jalinous, The Guide to Magnetic Stimulation, The Magstim Company Ltd, Spring Gardens, Whitland, Carmarthenshire, SA34 OHR, United Kingdom, 2006. In contrast, the magnetic stimulators that are disclosed herein are relatively simpler devices that use considerably smaller currents within the stimulator coils. Accordingly, they are intended to satisfy the need for simple-to-use and less expensive non-invasive magnetic stimulation devices, for use in treating gastroparesis or functional dyspepsia, as well as use in treating other conditions.
Potential advantages of such non-invasive medical methods and devices relative to comparable invasive procedures are as follows. The patient may be more psychologically prepared to experience a procedure that is non-invasive and may therefore be more cooperative, resulting in a better outcome. Non-invasive procedures may avoid damage of biological tissues, such as that due to bleeding, infection, skin or internal organ injury, blood vessel injury, and vein or lung blood clotting. Non-invasive procedures are generally painless and may be performed without the dangers and costs of surgery. They are ordinarily performed even without the need for local anesthesia. Less training may be required for use of non-invasive procedures by medical professionals. In view of the reduced risk ordinarily associated with non-invasive procedures, some such procedures may be suitable for use by the patient or family members at home or by first-responders at home or at a workplace. Furthermore, the cost of non-invasive procedures may be significantly reduced relative to comparable invasive procedures.
In the present invention, noninvasive electrical and/or magnetic stimulation of a vagus nerve is used to treat functional gastrointestinal disorders, which are defined as follows. Patients frequently consult a physician after experiencing gastrointestinal (GI) symptoms such as pain, nausea, vomiting, bloating, diarrhea, constipation, or difficult passage of food or feces. Tests are then performed in an effort to find an organic or structural explanation for the symptoms, such as an infection, tumor, structural blockage, metabolic abnormality or inflammation. When the tests do not reveal any such organic etiology or structural lesion, the patient is diagnosed as having a functional gastrointestinal disorder (FGID), which is to say, a GI disorder in which there is “no known structural (i.e, no pathological or radiological) abnormalities, or infectious, or metabolic causes”. Examples of FGIDs are irritable bowel syndrome, functional dyspepsia and chronic constipation.
Until about thirty years ago, functional gastrointestinal disorders were considered undiagnosed, uninvestigated, idiopathic or cryptogenic, or they were simply correlated with lifestyle or psychological influences such as excessive psychosocial stress, because no organic causes for their symptoms could be identified. In this regard, FGIDs share the absence of a straightforward, well-defined pathophysiological cause with other non-GI disorders, such as chronic fatigue syndrome, fibromyalgia, and chronic regional pain disorder [LEVY R L, Olden K W, Naliboff B D, Bradley L A, Francisconi C, Drossman D A, Creed F. Psychosocial aspects of the functional gastrointestinal disorders. Gastroenterology 130(5,2006):1447-1458; KIM S E, Chang L. Overlap between functional GI disorders and other functional syndromes: what are the underlying mechanisms? Neurogastroenterol Motil 24(10,2012):895-913; Clive H WILDER-SMITH. The balancing act: endogenous modulation of pain in functional gastrointestinal disorders. Gut 60(2011):1589-1599].
However, more recently, it is appreciated that a FGID is the clinical product of an interaction of psychosocial factors with an altered gut physiology that involves complex feedback between the gut and the central nervous system (the gut-brain axis). For example, some patients may experience a transient minor infection or inflammation in their GI tract that would not produce symptoms in a normal individual, but because the digestive and nervous systems of the FGID patient have become hypersensitive, the FGID patient does in fact develop GI symptoms [Douglas A. DROSSMAN. The functional gastrointestinal disorders and the Rome III process. Gastroenterology 130(2006):1377-1390; WOOD J D, Alpers D H, Andrews P L. Fundamentals of neurogastroenterology. Gut 45 (Supp) 2,1999):116-1116; GRUNDY D, Al-Chaer E D, Aziz Q, Collins S M, Ke M, Tache Y, Wood J D. Fundamentals of neurogastroenterology: basic science. Gastroenterology 130(5,2006):1391-1411; GEBHART G F. Pathobiology of visceral pain: molecular mechanisms and therapeutic implications IV. Visceral afferent contributions to the pathobiology of visceral pain. Am J Physiol Gastrointest Liver Physiol 278(6,2000):G834-838; CRAIG A D. How do you feel? Interoception: the sense of the physiological condition of the body. Nat Rev Neurosci 3(8,2002):655-666; BIELEFELDT K, Christianson J A, Davis B M. Basic and clinical aspects of visceral sensation: transmission in the CNS. Neurogastroenterol Motil 17(4,2005):488-499; MAYER E A, Naliboff B D, Craig A D. Neuroimaging of the brain-gut axis: from basic understanding to treatment of functional GI disorders. Gastroenterology 131(6,2006):1925-42; ANAND P, Aziz Q, Willert R, van Oudenhove L. Peripheral and central mechanisms of visceral sensitization in man. Neurogastroenterol Motil 19(1 Suppl, 2007):29-46; MAYER E A. The neurobiology of stress and gastrointestinal disease. Gut 47(6,2000):861-869; MAYER E A, Collins S M. Evolving pathophysiologic models of functional gastrointestinal disorders. Gastroenterology 122(7,2002):2032-2048; MAYER E A, Tillisch K, Bradesi S. Review article: modulation of the brain-gut axis as a therapeutic approach in gastrointestinal disease. Aliment Pharmacol Ther 24(6,2006):919-933; HOLZER P, Schicho R, Holzer-Petsche U, Lippe I T. The gut as a neurological organ. Wien Klin Wochenschr 113(17-18, 2001):647-60; MULAK A, Bonaz B. Irritable bowel syndrome: a model of the brain-gut interactions. Med Sci Monit 10(4,2004):RA55-RA62; JONES M P, Dilley J B, Drossman D, Crowell M D. Brain-gut connections in functional GI disorders: anatomic and physiologic relationships. Neurogastroenterol Motil 18(2,2006):91-103; MOSHIREE B, Zhou Q, Price D D, Verne G N. Central sensitisation in visceral pain disorders. Gut 55(7,2006):905-908; ZHOU Q, Verne G N. New insights into visceral hypersensitivity—clinical implications in IBS. Nat Rev Gastroenterol Hepato 8(6,2011):349-355].
The present invention is concerned primarily with a stomach-related type of FGID—functional dyspepsia, which has four specific symptoms that are thought to originate from the gastroduodenal region (viz., postprandial fullness, early satiation, epi-gastric pain, and epigastric burning). The invention is also concerned with a condition that is common among functional dyspepsia patients, in which there is delayed emptying of the stomach into the intestine. The medical term for such delayed stomach emptying in the absence of structural blockage is gastropareis (partial paralysis of the stomach), which is often accompanied by chronic or intermittent nausea, vomiting, early satiety, abdominal distention after eating, and/or abdominal pain typically following meals [MIWA H. Why dyspepsia can occur without organic disease: pathogenesis and management of functional dyspepsia. J Gastroenterol 47(8,2012):862-871; TACK J, Lee K J. Pathophysiology and treatment of functional dyspepsia. J Clin Gastroenterol 39(5 Suppl 3,2005):S211-6; TACK J, Masaoka T, Janssen P. Functional dyspepsia. Curr Opin Gastroenterol 27(6,2011):549-557; TACK J, Talley N J, Camilleri M, Holtmann G, Hu P, Malagelada J R, Stanghellini V. Functional gastroduodenal disorders. Gastroenterology 130(5,2006):1466-1479; Rita BRUN and Braden Kuo. Functional dyspepsia. Therap Adv Gastroenterol 3(3,2010): 145-164; AGREUS L. Natural history of dyspepsia. Gut 50 (Suppl 4,2002):iv2-9; GEERAERTS B, Tack J. Functional dyspepsia: past, present, and future. J Gastroenterol 43(4,2008): 251-255; LOYD R A, McClellan D A. Update on the evaluation and management of functional dyspepsia. Am Fam Physician 83(5,2011):547-552; HASLER W L. Gastroparesis: symptoms, evaluation, and treatment. Gastroenterol Clin North Am 36(3,2007):619-647; Olga HILAS. Management of Gastroparesis. US Pharm 36(12,2011):HS15-HS18; MASAOKA T, Tack J. Gastroparesis: current concepts and management. Gut Liver 3(3,2009):166-73; PATRICK A, Epstein O. Review article: gastroparesis. Aliment Pharmacol Ther. 2008 May; 27(9,2008):724-740; WASEEM S, Moshiree B, Draganov P V. Gastroparesis: current diagnostic challenges and management considerations. World J Gastroenterol 15(1,2009):25-37; VITTAL H, Farrugia G, Gomez G, Pasricha P J. Mechanisms of disease: the pathological basis of gastroparesis—a review of experimental and clinical studies. Nat Clin Pract Gastroenterol Hepatol 4(6,2007):336-346].
Despite the fact that at least some aspect each FDIG is different from the other FDIG disorders, they nevertheless may share other features, and they are frequently comorbid, so that they may be considered as a group. Furthermore, symptomatic and pathophysiological aspects that different FDIGs have in common may make it possible to treat them with similar therapeutic methods. Consequently, it is understood that the devices and methods of the present invention may be applicable to many types of FGID, as organized by the Rome III classification: A. Functional esophageal disorders (A1. Functional heartburn; A2. Functional chest pain of presumed esophageal origin; A3. Functional dysphagia; A4. Globus); B. Functional gastroduodenal disorders (B1. Functional dyspepsia; B1a. Postprandial distress syndrome; B1 b. Epigastric pain syndrome; B2. Belching disorders; B2a. Aerophagia; B2b. Unspecified excessive belching; B3. Nausea and vomiting disorders;B3a. Chronic idiopathic nausea; B3b. Functional vomiting; B3c. Cyclic vomiting syndrome; B4. Rumination syndrome in adults or Merycism); C. Functional bowel disorders (C1. Irritable bowel syndrome; C2. Functional bloating; C3. Functional constipation; C4. Functional diarrhea; C5. Unspecified functional bowel disorder; D. Functional abdominal pain syndrome; E. Functional gallbladder and Sphincter of Oddi (SO) disorders (E1. Functional gallbladder disorder; E2. Functional biliary SO disorder; E3. Functional pancreatic SO disorder); F. Functional anorectal disorders (F1. Functional fecal incontinence; F2. Functional anorectal pain; F2a. Chronic proctalgia; F2a1. Levator ani syndrome; F2a2. Unspecified functional anorectal pain; F2b. Proctalgia fugax; F3. Functional defecation disorders; F3a. Dyssynergic defecation; F3b. Inadequate defecatory propulsion; G. Various GI functional disorders in neonates and toddlers; and H. Various functional GI disorders in children and adolescents.
FGIDs account for 41% of diagnoses in GI specialty practices, among which irritable bowel syndrome (IBS) is the most common. IBS comprises 12% of the diagnoses made by primary care physicians generally and 28% of the diagnoses in GI practices. Its prevalence is in the range 5-25%, and it accounts for 36% of all visits to gastroenterologists [CHANG L. Review article: epidemiology and quality of life in functional gastrointestinal disorders. Aliment Pharmacol Ther 20 (Suppl 7,2004):31-39; DROSSMAN D A, Li Z, Andruzzi E, et al. U.S. householder survey of functional gastrointestinal disorders. Prevalence, sociodemography, and health impact. Dig Dis Sci. 38(9,1993):1569-1580; MERTZ H R. Irritable bowel syndrome. N Engl J Med 349(22,2003):2136-2146; CAMILLERI M. Treating irritable bowel syndrome: overview, perspective and future therapies. Br J Pharmacol 141(8,2004):1237-1248; DROSSMAN D A. Review article: an integrated approach to the irritable bowel syndrome. Aliment Pharmacol Ther 13 (Suppl 2,1999):3-14].
Dyspepsia also has a high prevalence. Patients often experience dyspeptic symptoms of short duration and mild severity, and are therefore self-managed, with less than half of dyspepsia sufferers seeking medical care for their complaints. Even so, there are over 2 million physician consultations for dyspepsia annually in the United States alone. Dyspepsia has a prevalence of approximately 25% in Western countries, even after the exclusion of individuals with typical gastro-esophageal reflux disease (GERD) symptoms. The annual incidence of dyspepsia is approximately 9-10%, and 15% of patients have chronic (>3 months in a year), frequent (>3 episodes per week) often severe symptoms. Functional dyspepsia is the most common cause of dyspeptic symptoms (approximately 75%), with the remainder of dyspepsia cases having an organic cause such as a peptic ulcer, reflux disease, etc. [Andrew Seng Boon CHUA. Epidemiology of functional dyspepsia: A global perspective. World J Gastroenterol 12(17,2006): 2661-2666; SHAIB Y, El-Serag H B. The prevalence and risk factors of functional dyspepsia in a multiethnic population in the United States. Am J Gastroenterol 99(11,2004):2210-2216; OUSTAMANOLAKIS P, Tack J. Dyspepsia: organic versus functional. J Clin Gastroenterol 46(3,2012):175-90; SANDER G B, Mazzoleni L E, Francesconi C F, et al. Influence of organic and functional dyspepsia on work productivity: the HEROES-DIP study. Value in Health14(5 Suppl 1, 2011):5126-5129].
A difficulty in interpreting the epidemiological data mentioned above is that considerable symptomatic and pathophysiological overlap exists between FDIG disorders. Thus, despite their classification as different entities, IBS and functional dyspepsia may also be regarded as different manifestations of a larger pathophysiological entity that encompasses even non-FGID disorders with which the FDIG disorders may be comorbid, such as overactive bladder [FRISSORA C L, Koch K L. Symptom overlap and comorbidity of irritable bowel syndrome with other conditions. Curr Gastroenterol Rep 7(4,2005):264-271; Laura NODDIN, Michael Callahan, and Brian E. Lacy. Irritable Bowel Syndrome and Functional Dyspepsia: Different Diseases or a Single Disorder With Different Manifestations? Med Gen Med 7(3,2005): 17, pp. 1-10; WANG A, Liao X, Xiong L, Peng S, Xiao Y, Liu S, Hu P, Chen M. The clinical overlap between functional dyspepsia and irritable bowel syndrome based on Rome III criteria. BMC Gastroenterol 8(2008): 43, pp. 1-7; BALBOA A, Mearin F, Badia X, et al. Impact of upper digestive symptoms in patients with irritable bowel syndrome. Eur J Gastroenterol Hepatol 18(12,2006):1271-1277; DEVRIES D R, Van Herwaarden M A, Baron A, Smout A J, Samsom M. Concomitant functional dyspepsia and irritable bowel syndrome decrease health-related quality of life in gastroesophageal reflux disease. Scand J Gastroenterol 42(8,2007):951-956; EVANS P R, Bak Y T, Shuter B, Hoschl R, Kellow J E. Gastroparesis and small bowel dysmotility in irritable bowel syndrome. Dig Dis Sci 42(10,1997):2087-2093; QUIGLEY E M. Review article: gastric emptying in functional gastrointestinal disorders. Aliment Pharmacol Ther 20 (Suppl 7,2004):56-60; A R O P, Talley N J, Ronkainen J, Storskrubb T, Vieth M, Johansson S E, Bolling-Sternevald E, Agréus L. Anxiety is associated with uninvestigated and functional dyspepsia (Rome III criteria) in a Swedish population-based study. Gastroenterology 137(1,2009):94-100; HSU Y C, Liou J M, Liao S C, Yang T H, Wu H T, Hsu W L, Lin H J, Wang H P, Wu M S. Psychopathology and personality trait in subgroups of functional dyspepsia based on Rome III criteria. Am J Gastroenterol 104(10,2009):2534-2542; SANTONICOLA A, Siniscalchi M, Capone P, Gallotta S, Ciacci C, lovino P. Prevalence of functional dyspepsia and its subgroups in patients with eating disorders. World J Gastroenterol. 18(32,2012):4379-4385; MATSUZAKI J, Suzuki H, Fukushima Y, Hirata K, Fukuhara S, Okada S, Hibi T. High frequency of overlap between functional dyspepsia and overactive bladder. Neurogastroenterol Motil 24(9,2012):821-827].
Similarly, the distinction between functional dyspepsia and gastroparesis is equivocal. Gastroparesis is a syndrome characterized by delayed gastric emptying in the absence of mechanical obstruction. The main symptoms include early satiety, nausea, vomiting, pain, and bloating. In one study, the frequency of symptoms was pain (89%), nausea (93%), early satiety (86%) and vomiting (68%). Gastroparesis is common, affecting up to 5 million individuals in the United States. The majority of patients are female (80%) and the mean age of onset is 34 years. Between 5 and 12 percent of patients with diabetes have symptoms that are attributable to gastroparesis [Baha MOSHIREE, Steven Bollipo, Michael Horowitz, and Nicholas J. Talley. Epidemiology of gastroparesis. Chapter 2 (pp. 11-22) In: Gastroparesis. Pathophysiology, Presentation and Treatment. H. P. Parkman and R. W. McCallum, eds. New York: Humana Press, 2012; JUNG H K, Choung R S, Locke G R 3rd, Schleck C D, Zinsmeister A R, Szarka L A, Mullan B, Talley N J. The incidence, prevalence, and outcomes of patients with gastroparesis in Olmsted County, Minnesota, from 1996 to 2006. Gastroenterology 136(4,2009):1225-1233].
Gastroparesis is primarily (but not exclusively) a motility disorder of the stomach, in contrast to functional dyspepsia (FD), which is a functional disorder of the stomach with intertwined sensory and motility abnormalities. Nevertheless, although gastroparesis and FD are generally considered two distinct disorders, the distinction between them is blurred by the considerable overlap in symptoms and the recognition that delayed gastric emptying can be seen in FD. The symptoms of FD are directly caused by two major physiological abnormalities—abnormal gastric motility and visceral hypersensitivity—occurring in patients who have acquired excessive responsiveness to stress as a result of the environment during early life, genetic abnormalities, residual inflammation after gastrointestinal infections, or other causes, with the process modified by factors including psychophysiological abnormalities, abnormal secretion of gastric acid, Helicobacter pylori infection, diet, and lifestyle. Accordingly, the current (Rome III) diagnostic criteria subdivides FD into two categories—(i) meal-induced dyspeptic symptoms (post-prandial distress syndrome [PDS], characterized by postprandial fullness and early satiation) and (ii) epigastric pain syndrome ([EPS], characterized by epi-gastric pain and burning). A rationale for the subdivision is that different treatment modalities may be most suitable for each subgroup: acid suppressive therapy in EPS, and therapy for PDS in which drugs are used to increase gastrointestinal movement (prokinetic therapy). Therefore, gastroparesis may be most closely associated with the PDS category of functional dyspepsia. In fact, some patients with mild abdominal pain, nausea, postprandial distress, and evidence of delayed emptying are considered to have functional dyspepsia by some clinicians and gastroparesis by others, based on a subjective assessment of how much visceral hypersensitivity versus dysmotility contributes to the symptoms. From a diagnostic standpoint, a presentation of predominant pain and less nausea is considered to be more typical of functional dyspepsia, whereas dominant nausea with minimal pain is more consistent with idiopathic gastroparesis [PARKMAN H P, Camilleri M, Farrugia G, et al. Gastroparesis and functional dyspepsia: excerpts from the AGA/ANMS meeting. Neurogastroenterol Motil 22(2,2010):113-133; TALLEY N J, Locke G R 3rd, Lahr B D, Zinsmeister A R, Tougas G, Ligozio G, Rojavin M A, Tack J. Functional dyspepsia, delayed gastric emptying, and impaired quality of life. Gut 55(7,2006):933-9; KINDT S, Dubois D, Van Oudenhove L, Caenepeel P, Arts J, Bisschops R, Tack J. Relationship between symptom pattern, assessed by the PAGI-SYM questionnaire, and gastric sensorimotor dysfunction in functional dyspepsia. Neurogastroenterol Motil 21(11,2009):1183-1188 and e104-e105; John M. W O and Henry P. Parkman. Motility and Functional Disorders of the Stomach: Diagnosis and Management of Functional Dyspepsia and Gastroparesis. Practical Gastroenterology. December 2006: 23-48; STANGHELLINI V, De Giorgio R, Barbara G, Cogliandro R, Tosetti C, De Ponti F, Corinaldesi R. Delayed Gastric Emptying in Functional Dyspepsia. Curr Treat Options Gastroenterol 7(4,2004):259-264].
In the remainder of this background section, current methods for treating functional dyspepsia and gastroparesis are described. As summarized here, they include pharmacological methods, the use of herbal medicines, biofeedback and breathing exercises, hypnosis, acupuncture, direct electrical stimulation of the stomach (gastric electrical stimulation or GES), direct electrical stimulation of the intestine, invasive vagus nerve stimulation, and deep brain stimulation. As evidenced by the large number of potential treatment methods that are in use, none of them works reliably, which motivates the new and potentially better methods that are disclosed here [TALLEY N J, Vakil N; Practice Parameters Committee of the American College of Gastroenterology. Guidelines for the management of dyspepsia. Am J Gastroenterol 100(10,2005):2324-2337; North of England Dyspepsia Guideline Development Group. Dyspepsia. Managing dyspepsia in adults in primary care. Centre for Health Services Research. University of Newcastle upon Tyne. 21 Claremont Place. Newcastle upon Tyne. NE24AA. UK. 2004, pp. 1-288; SAAD R J, Chey W D. Review article: current and emerging therapies for functional dyspepsia. Aliment Pharmacol Ther 24(3,2006):475-492; HASLER W L. Gastroparesis: symptoms, evaluation, and treatment. Gastroenterol Clin North Am 36(3,2007):619-647; Olga HILAS. Management of Gastroparesis. US Pharm 36(12,2011):HS15-HS18; MASAOKA T, Tack J. Gastroparesis: current concepts and management. Gut Liver 3(3,2009):166-73; WASEEM S, Moshiree B, Draganov P V. Gastroparesis: current diagnostic challenges and management considerations. World J Gastroenterol 15(1,2009):25-37].
Dietary approaches to treatment involve ingesting multiple small meals each day and consuming more liquid and less solid. Fatty food and carbonated beverages are avoided, and for patients who are diabetic, their diet is modified to treat the diabetes.
No drugs with established efficacy are definitive for treatment of functional dyspepsia and gastroparesis. However, gastrointestinal prokinetic drugs, which stimulate gastric smooth muscle contractions, have long been considered the drugs of choice. Traditional prokinetic agents are dopamine-2-receptor (D2) antagonists or 5-HT4 receptor agonists, e.g., cisapride (but now withdrawn from the market), domperidone, metoclopramide, and mosapride. Erythromycin is also used to enhance motility. H2 receptor antagonists, proton pump inhibitors, antiemetics and drugs to treat H. Pylori are also sometimes prescribed [TACK J, Lee K J. Pathophysiology and treatment of functional dyspepsia. J Clin Gastroenterol 39(5 Suppl 3,2005):5211-6; MONKEMULLER K, Malfertheiner P. Drug treatment of functional dyspepsia. World J Gastroenterol 12(17,2006):2694-2700; HASLER W L. Gastroparesis: symptoms, evaluation, and treatment. Gastroenterol Clin North Am 36(3,2007):619-647].
Alternative medicine approaches are also used to treat functional dyspepsia and gastroparesis, including the use of herbal medicines, biofeedback, and hypnosis [Thompson COON J, Ernst E. Systematic review: herbal medicinal products for non-ulcer dyspepsia. Aliment Pharmacol Ther 16(10,2002):1689-1699; HJELLAND I E, Svebak S, Berstad A, Flatabφ G, Hausken T. Breathing exercises with vagal biofeedback may benefit patients with functional dyspepsia. Scand J Gastroenterol 42(9,2007):1054-1062; CALVERT E L, Houghton L A, Cooper P, Morris J, Whorwell P J. Long-term improvement in functional dyspepsia using hypnotherapy. Gastroenterology 123(6,2002):1778-85].
Acupuncture is also used to treat functional dyspepsia and gastroparesis. The sites of stimulation are usually RN12 (at the middle of the stomach), ST36 (on the front of the leg), PC6 (located on the wrist), and SP6 (on the medial aspect of the lower leg) [TAKAHASHI T. Acupuncture for functional gastrointestinal disorders. J Gastroenterol 41(5,2006):408-417; ZHENG H, Tian X P, Li Y, Liang F R, et al. Acupuncture as a treatment for functional dyspepsia: design and methods of a randomized controlled trial. Trials 10(2009):75, pp. 1-9; KIM K H, Kim T H, Choi J Y, Kim J I, Lee M S, Choi S M. Acupuncture for symptomatic relief of gastroparesis in a diabetic haemodialysis patient. Acupunct Med 28(2,2010):101-103; WANG C P, Kao C H, Chen W K, Lo W Y, Hsieh C L. A single-blinded, randomized pilot study evaluating effects of electroacupuncture in diabetic patients with symptoms suggestive of gastroparesis. J Altern Complement Med 14(7,2008):833-839; IMAI K, Ariga H, Chen C, Mantyh C, Pappas T N, Takahashi T. Effects of electroacupuncture on gastric motility and heart rate variability in conscious rats. Auton Neurosci 138(1-2,2008):91-98]. Despite the fact that a vagus nerve is not stimulated by the acupuncture as currently practiced, vagal activity is nevertheless said to be indirectly affected [OUYANG H, Yin J, Wang Z, Pasricha P J, Chen J D. Electroacupuncture accelerates gastric emptying in association with changes in vagal activity. Am J Physiol Gastrointest Liver Physiol 282(2,2002):G390-G396].
Various devices have been used or proposed to treat functional gastrointestinal disorders and gastroparesis [GREENWAY F, Zheng J. Electrical stimulation as treatment for obesity and diabetes. J Diabetes Sci Technol 1(2,2007):251-259]. The most well known among them is gastric electrical stimulation (GES), which stimulates stomach muscle directly, in a manner that is analogous to a cardiac pacemaker. Low-frequency/high-energy GES appears to work well in principle, but it is not presently suitable for routine clinical use. High-frequency/low-energy GES does not significantly modify gastric slow wave and motor activity and does not appear to consistently resolve the problem of delayed gastric emptying, but may it nevertheless resolve some symptoms. Therefore, GES is considered at best partially successful in treating gastroparesis [Mauro BORTOLOTTI. Gastric electrical stimulation for gastroparesis: A goal greatly pursued, but not yet attained. World J Gastroenterol 17(3,2011): 273-282; McCALLUM R W, Dusing R W, Sarosiek I, Cocjin J, Forster J, Lin Z. Mechanisms of symptomatic improvement after gastric electrical stimulation in gastroparetic patients. Neurogastroenterol Motil 22(2,2010):161-167, e50-e51; YIN J, Abell T D, McCallum R W, Chen J D. Gastric neuromodulation with Enterra system for nausea and vomiting in patients with gastroparesis. Neuromodulation 15(3,2012):224-231; SOFFER E, Abell T, Lin Z, Lorincz A, McCallum R, Parkman H, Policker S, Ordog T. Review article: gastric electrical stimulation for gastroparesis—physiological foundations, technical aspects and clinical implications. Aliment Pharmacol Ther 30(7,2009):681-694; SONG G Q, Chen J D. Synchronized gastric electrical stimulation improves delayed gastric emptying in nonobese mice with diabetic gastroparesis. J Appl Physiol 103(5,2007):1560-1564; LIU J, Qiao X, Chen J D. Vagal afferent is involved in short-pulse gastric electrical stimulation in rats. Dig Dis Sci 49(5,2004):729-737; CHEN J H, Song G Q, Yin J, Sun Y, Chen J D. Gastric electrical stimulation reduces visceral sensitivity to gastric distention in healthy canines. Auton Neurosci 160(1-2,2011):16-20; OGRADY G, Egbuji J U, Du P, Cheng L K, Pullan A J, Windsor J A. High-frequency gastric electrical stimulation for the treatment of gastroparesis: a meta-analysis. World J Surg 33(8,2009):1693-1701]. GES is also disclosed in the patent literature, for example: U.S. Pat. No. 8,239,027, entitled Responsive gastric stimulator, to IMRAN; and U.S. Pat. No. 7,363,084, entitled Device for electrically stimulating stomach, to KUROKAWA et al.
In some patients, delayed emptying of the stomach may be due in part to delayed movement of chyme in the intestine, i.e., a downstream backing-up, such that intestinal movement that is promoted by electrical stimulation of the intestine itself may indirectly promote gastric emptying [XU J, Chen J D. Intestinal electrical stimulation improves delayed gastric emptying and vomiting induced by duodenal distension in dogs. Neurogastroenterol Motil 20(3,2008):236-42]. As described below, a related mechanism is invoked by KNUDSEN et al in the form of “enteric rhythm management”, wherein invasive vagus nerve stimulation is used to promote the effects of pancreatic exocrine secretion and bile on the composition and the digestion of intraduodenal chyme, thereby indirectly promoting gastric emptying through downstream effects. The present invention uses noninvasive rather than invasive vagus nerve stimulation, and physiological differences as compared with the KNUDSEN disclosure also arise because the present invention stimulates the vagus nerve at a different location and involves different mechanisms, but it is understood that the present invention might also produce such coordinated effects throughout the gastrointestinal system, thereby also underscoring the overlap between different forms of functional gastrointestinal disorders.
Deep brain electrical stimulation has also been used in connection with gastrointestinal problems, but only in conjunction with the treatment of another problem such as parkinsonism [ARAI E, Arai M, Uchiyama T, et al. Subthalamic deep brain stimulation can improve gastric emptying in Parkinson's disease. Brain 135 (Pt 5,2012):1478-1485].
Magnetic stimulation of patients with gastrointestinal disorders has apparently not been performed for dyspepsia or gastroparesis, although it has been performed for lower digestive problems (on the buttocks) and for visceral pain (at the cerebral cortex) [LEE K J, Kim J H, Cho S W. Short-term effects of magnetic sacral dermatome stimulation for idiopathic slow transit constipation: sham-controlled, cross-over pilot study. J Gastroenterol Hepatol 21(1 Pt 1,2006):47-53; LEFAUCHEUR J P. Use of repetitive transcranial magnetic stimulation in pain relief. Expert Rev Neurother 8(5,2008):799-808].
The literature on vagus nerve stimulation (VNS) generally teaches that its use may produce adverse gastrointestinal side effects, which is to say, most of the VNS literature teaches away from the present invention. Thus, nausea (14-20%), vomiting (13-18%) and dyspepsia (12-18%) are commonly reported adverse effects from implanted vagus nerve stimulators that are used to treat epilepsy and/or depression, although the side-effects are generally mild and usually do not warrant termination of the therapy. The prevalence of the side effects depends upon the parameters of the nerve stimulation (frequency, pulse-width, etc.). There is also one case report in which chronic diarrhea was associated with VNS, such that the diarrhea ceased after VNS therapy was terminated [HATTON K W, McLarney J T, Pittman T, Fahy B G. Vagal nerve stimulation: overview and implications for anesthesiologists. Anesth Analg 103(5,2006):1241-1249; SANOSSIAN N, Haut S. Chronic diarrhea associated with vagal nerve stimulation. Neurology 58(2002):330].
Nevertheless, SINCLAIR reported one clinical case demonstrating that invasive VNS might offer an alternative solution to dyspepsia resulting from impaired gastric emptying, or at least a treatment for symptoms of reflux [Rohna SINCLAIR and Rahul R. Bajekal. Vagal Nerve Stimulation and Reflux. Anesthesia & Analgesia 105(3, 2007): 884-885]. Invasive VNS to treat gastrointestinal conditions is also described in several patents. In U.S. Pat. No. 5,540,730, entitled Treatment of motility disorders by nerve stimulation, to TERRY, Jr. et al., stimulation of a vagus nerve in the vicinity of the patient's stomach is performed in response to the impedance of a selected part of the gastrointestinal system (as an indication of gastrointestinal status), in order to treat hypomobility or hypermobility. In U.S. Pat. No. 7,167,751, entitled Method of using a fully implantable miniature neurostimulator for vagus nerve stimulation to WHITEHURST et al. it is disclosed that: “As another example, the vagus nerve may be stimulated to relieve gastrointestinal disorders (such as including gastroesophageal reflux disease (GERD), fecal dysfunction, gastrointestinal ulcer, gastroparesis, and other gastrointestinal motility disorders.” In U.S. Pat. No. 7,856,273, entitled Autonomic nerve stimulation to treat a gastrointestinal disorder, to MASCHINO et al., a vagus nerve is electrically stimulated in order to treat a gastrointestinal disorder that may include a motility disorder. Invasive vagus nerve stimulation has also been combined with gastric electrical stimulation (GES) [U.S. Pat. No. 6,826,428, entitled Gastrointestinal electrical stimulation, to CHEN et al.].
In a series of patents and patent applications, KNUDSON and colleagues also describe invasive methods in which a vagus nerve is electrically stimulated in order to treat a variety of functional gastrointestinal disorders [All to KNUDSON et al.—U.S. Pat. No. 8,046,085, entitled Controlled vagal blockage therapy; U.S. Pat. No. 8,010,204, entitled Nerve blocking for treatment of gastrointestinal disorders; U.S. Pat. No. 7,986,995, entitled Bulimia treatment; U.S. Pat. No. 7,729,771, entitled Nerve stimulation and blocking for treatment of gastrointestinal disorders; U.S. Pat. No. 7,720,540, entitled Pancreatitis treatment; U.S. Pat. No. 7,693,577, entitled Irritable bowel syndrome treatment; U.S. Pat. No. 7,630,769, entitled GI inflammatory disease treatment; U.S. Pat. No. 7,489,969, entitled Vagal down-regulation obesity treatment; U.S. Pat. No. 7,444,183, entitled Intraluminal electrode apparatus and method; U.S. Pat. No. 7,167,750, entitled Obesity treatment with electrically induced vagal down regulation; U.S. Pat. No. 7,844,338, entitled High frequency obesity treatment; U.S. Pat. No. 7,613,515, entitled High frequency vagal blockage therapy; US 20040176812, entitled Enteric rhythm management; US 20040172085, entitled Nerve stimulation and conduction block therapy]. These patents and applications differ from the present invention in several significant ways, including: they involve invasive methods, whereas the present invention involves noninvasive methods; in those patents, the site of vagus nerve stimulation is below a vagal innervation of the heart, e.g. a few centimeters below the diaphragm and proximal to stomach and pancreo/biliary innervation or around an internal body organ, whereas the present invention stimulates a vagus nerve at the neck, such that different vagal nerve fibers are stimulated in the present invention; stimulation in the present invention may generate proximate effects within the central nervous system (e.g., increasing afferent activity in A and B fibers of the vagus nerve to increase the levels of inhibitory neurotransmitters in the brainstem), whereas they produce their proximate effects within a gastrointestinal end organ through efferent nerves; they generally involve the use of one or more blocking electrodes (functionally speaking, a reversible vagotomy, wherein the block at least partially prevents nerve transmission across the site of the block), whereas the present invention does not; the present invention makes use of a bursting sinusoidal stimulation signal, whereas they do not; with regard to effects on gastric emptying, the present invention modulates the activity of interstitial cells of Cajal, whereas they do not; the present invention may modify resting state neural networks in the brain that are related to interoception, whereas they do not disclose any such mechanism. Many of these same distinctions apply to the other previously mentioned invasive VNS patents as well.
There also exists literature concerning noninvasive electrical stimulation methods as they relate to gastrointestinal disorders. Noninvasive methods have been described to treat symptoms that may accompany functional gastrointestinal disorders, e.g., nausea and vomiting. U.S. Pat. No. 4,865,048, entitled Method and apparatus for drug free neurostimulation, to ECKERSON, teaches electrical stimulation of a branch of the vagus nerve behind the ear on the mastoid processes, in order to treat symptoms of drug withdrawal that may include nauses (sic) and vomiting. In patent publication US20080208266, entitled System and method for treating nausea and vomiting by vagus nerve stimulation, to LESSER et al., electrodes are used to stimulate the vagus nerve in the neck to reduce nausea and vomiting, or can be arranged near the chest or abdomen, so as to stimulate the esophagus, stomach, duodenum or intestines. However, because these methods are intended to treat morning sickness, side-effects of chemotherapy, etc., they are not designed specifically for treating for the forms of nausea and vomiting that are due to dyspepsia, gastroparesis, or other functional gastrointestinal disorders and do not simultaneously treat other symptoms of those disorders such as bloating. Consequently, those methods are intended to treat nausea and vomiting, but not a gastrointestinal disorder per se. For example, patients with gastroparesis, cyclic vomiting syndrome, and rumination syndrome may all experience different forms of vomiting, but the ECKERSON and the LESSER disclosures do not suggest which, if any, of these disorders may be treated by their methods. Furthermore, they teach devices and stimulation parameters that differ from what is disclosed here.
In contrast, WEINKAUF and colleagues used transcutaneous electrical stimulation to treat true gastroparesis. However, unlike the present invention, the electrical stimulation was performed on the back of the patients and did not involve the vagus nerve [WEINKAUF J G, Yiannopoulos A, Faul J L. Transcutaneous electrical nerve stimulation for severe gastroparesis after lung transplantation. J Heart Lung Transplant. 24(9,2005):1444.e1-e3]. Similarly, KOKLU and colleagues used transcutaneous interferential current electrical stimulation to treat dyspeptic patients. However, also unlike the present invention, the electrical stimulation was performed on the back of the patients and did not involve stimulating a selected vagus nerve [KOKLU S, KöklüG, Ozgüçclü E, Kayani G U, Akbal E, Hascelik Z. Clinical trial: interferential electric stimulation in functional dyspepsia patients—a prospective randomized study. Aliment Pharmacol Ther 31(9,2010):961-968]. Patent publication US20100249859, entitled Methods for autonomic neuromodulation for the treatment of systemic disease, to DiLorenzo, discloses that “Modulation [of cranial nerves] is performed to modulate . . . gastroparesis, and other disorders.” He includes noninvasive techniques among those used for neural modulation, but described them only as being the use of tactile stimulation, including light touch, pressure, vibration, and other modalities that may be used to activate the peripheral or cranial nerves. BALAJINS also describes noninvasive stimulation of the vagus nerve in the context of gastroenterology, but the stimulation involves sham feeding rather than electrical stimulation [BALAJI NS, Crookes P F, Banki F, Hagen J A, Ardill J E, DeMeester T R. A safe and noninvasive test for vagal integrity revisited. Arch Surg 137(8,2002): 954-958; LUNDING J A, Nordstrom L M, Haukelid A O, Gilja O H, Berstad A, Hausken T. Vagal activation by sham feeding improves gastric motility in functional dyspepsia. Neurogastroenterol Motil 20(6,2008):618-624]. In view of the foregoing, noninvasive electrical stimulation of a vagus nerve at the neck has not been performed to treat gastroparesis, functional dyspepsia, or other functional gastrointestinal conditions, despite the aforementioned potential advantages of noninvasive methods as compared with invasive methods.
In a commonly assigned, co-pending patent application, US20110125203, entitled Magnetic Stimulation Devices and Methods of Therapy, to SIMON et al., Applicants teach the use of a magnetic stimulation device, such as the ones disclosed here, to stimulate a vagus nerve in the neck to treat postoperative ileus, which is a form of hypomotility of the gastrointestinal tract in the absence of mechanical bowel obstruction. In that application, Applicants also teach use of a magnetic stimulation device to treat sphincter of Oddi dysfunction by stimulating a nerve plexus of fibers emanating from the tenth cranial nerve (the vagus nerve). In another commonly assigned, co-pending patent application, US20120101326, entitled Non-invasive electrical and magnetic nerve stimulators used to treat overactive bladder and urinary incontinence, to SIMON et al., applicants disclose the use of electrical nerve stimulation to affect pacemaker cells in the bladder that resemble the pacemaker cells in the stomach (interstitial cells of Cajal). The present disclosure extends those teachings to include additional methods and devices for the treatment or prevention of functional gastrointestinal disorders and gastroparesis.